Michael O'Leary said the airline had revived inquiries into whether the airline could install coin-operated toilets on its fleet.

"People might actually have to spend a pound to spend a penny in future," he said in a BBC interview, adding "We're always in Ryanair looking at the ways of constantly lowering the costs of air travel and making it more affordable and easier for passengers to fly with us."

Asked by the incredulous presenter what passengers would do if they found themselves without money mid-flight, O'Leary replied: "I don't think there is anybody in history that has got on board a Ryanair aircraft with less than a pound." Sound Off: Is it fair to charge a fee for a flush?

The Irish airline is renowned for its cheap flights and regularly advertises competition-crushing deals to boost capacity on its short-haul routes.